“I came to Philena when I was in a very dark place. Through her patience, guidance and gentleness, I genuinely left feeling hopeful. She held me together emotionally and spiritually throughout this time. She lit the candle in my mind and let my spirit guide me to light. She has a wonderful personality and in my heart I know our paths were meant to cross.”

And when the testimonial is given by a celebrity, people are especially susceptible. Often, the name of a famous person will attract consumers in droves to whatever product is being peddled, even if the celebrity endorser has no relevant knowledge that would allow them to evaluate the product with any more expertise than an ordinary person.

The influence of celebrity testimonials, and our infatuation with celebrities generally, probably have their roots in humanity’s evolutionary heritage. The earliest human societies, like those of our ape-like ancestors, were small hunter-gatherer bands where individuals could rise or fall in status depending on their ability to sway the group. Although the rewards of being the group leader sowed the seeds of ambition in all of us, the tribe had to have stability for the sake of all its members’ survival, which is why humans also have an inbuilt instinct to respect the authority of the alpha male or alpha female.

In modern society, where our social networks are vastly farther-ranging, celebrities have stepped into the role of alphas. We look up to them because, in a sense, we’re programmed to do so. This is a predisposition that can be resisted through reason, but not if we’re not aware of it.

The key thing to keep in mind about all testimonials is that, at best, they are anecdotal evidence. When it comes to alternative medicine, for instance, most diseases and injuries heal on their own. But if you just happen to be taking some dubious remedy when you begin feeling better, most people will credit their recovery to the treatment. Even a treatment that actually helps some people may be ineffective in others for any of a wide variety of reasons. And people who’ve already been persuaded of the efficacy of a treatment are much more likely to report positive results, and disregard any negative outcome that doesn’t fit with their expectations.

For all these reasons, isolated anecdotes are of no value in judging the usefulness of any dubious claim. At most, they may be an indicator of which avenues might reward further exploration. At worst, they are outright deceptive, leading naive people to expect outcomes that are extremely unlikely. To truly judge the worth of a claim, we need statistical evidence that gives a genuine measure of likelihood that it will work. Thus, it’s good news that the FTC is mulling requiring advertisers to report the average person’s benefit from their product, rather than relying on “results not typical” testimonials. Marketers may howl, but in the long run it will help people make informed decisions and move the market as a whole in a more rational direction.

Adam Lee of Daylight Atheism

Adam Lee is an atheist writer and speaker living in New York City. He created Daylight Atheism to push back against undeserved privileging of religion and to encourage atheists to step out of their closets, into the daylight, and take our rightful place at the table of society’s discourse.